DE10315906B4 - Device for distributing plastic plastic material - Google Patents

Abstract

Molten polymer flows from the entry (2) to the exit (3) through an initial pre-distributor (4) to a fine distributor (5), which can be a sieve plate or mesh ring. The pre-distributor (4) is in the shape of a spigot and has a main passage (7) leading into spiral branches (8). Additional spiral branches of the opposite hand can be added to intersect the other spiral branches.

Description

The The invention relates to a device for distributing plastic Plastic compound in an extrusion tool, in particular pipe extrusion tool, comprising a melt inlet and at least one melt outlet, wherein between the melt inlet and the melt outlet first Pre-distribution element and then a Feinverteilelement is arranged in the form of a screen basket.

to Production of pipes, it is necessary that of an extruder generated cylindrical Plastic melt stream using a subsequent tool in an annular gap-shaped Transform melt stream. Therefor It is important that the melt stream coming from the extruder is in the Tool through a centrally arranged mandrel in the corresponding Ring flow is transferred.

Around It is necessary to fix the mandrel mechanically in the tool to be fastened to the outer tool housing with the help of connecting elements. The connecting elements share the melt flow coming from the extruder in at least two strands which are subsequently combined again by appropriate methods. In polyolefins with large Memory effect are spiral distributors and baskets the most common Aids.

The Spiral distributors usually achieve good axial and radial Mixing of the distribution streams without tie lines, have to but in their geometric design to the respective flow behavior be adapted to the polyolefins. Disadvantages of this tool system are thus to be seen in the complex dimensioning of the melt guide channels, their reason in the big one Number of correlated geometry parameters. This restricts the possible use of a Spiral distributor over the size Range of polyolefin types significantly.

spiral distributor with relatively deep coils experience has shown that they can be used more universally, to lead but to a high residence time of the melt in the deep helical turns. Farther is in this form of execution both the residence time of the individual flow paths and the shear rate range the individual melt particles highly heterogeneous. The aforementioned inhomogeneities lead to different temperatures in the melt as well as to build of orientation states and finally affect disadvantageous in the tube quality out.

Siebkorbwerkzeuge have in tube extrusion basically the same task as Spiral mandrel dies. The baskets allow due to their construction a double deflection of the melt stream, so that also here a very good mixing and homogenization of the melt takes place. In contrast to the spiral distributors, they are more universal in polyolefins used. Furthermore, the average residence time is relatively short, but also the total width of the Verweilsspektrums, as a hallmark for the Self-cleaning, for the production acceptable. Due to the overall design of the Siebkorbprinzips the range of high melting shear is limited to the sieve segment, whereby the dissipative temperature increase low fails, and thus also the temperature spectrum of the individual melt particles is relatively constant.

Distribution systems are already known in the prior art DE 198 46 158 A1 For example, an extrusion tool with a displacement body which is fixed by holders. The disclosed therein new mandrel holder minimizes the weld lines, as the holder for the displacer was solved in the form of a basket, the opening facing the extruder.

Also the DE 11 82 420 B shows an extruder head with mandrel. Here, the mandrel is connected via a mandrel holder with a cavity formed by a mouthpiece and a mandrel on doubly deflected paths. By this considerable design effort to achieve virtually mark-free dimensionally stable pipes.

improvement offers the previous design of the inflow channel. The from the distribution wells delivered melt streams flow in a torus, from which perpendicular to the extrusion direction of the Strainer basket is supplied with material. The melt is subject to transition from inflow channel to the annulus no clear positive guidance and thus allows the individual melt particles, very different flow paths to follow. The preferred direction of the melt streams in the extrusion direction is formed by the distribution wells. In addition to these form, in Direction of rotation of the torus cross-section, flows from around the annulus to fill. The expression the cross flow corresponds to the adjusting isobaric curves in the torus.

task The invention is therefore to provide a pre-distribution for the screen basket, in which the melt clearly in the annulus before and below the Sieve basket out becomes.

The solution the object is in connection with the preamble of the claim 1 characterized in that the Pre-distribution element is designed as a mandrel and a main channel comprises, which is in fluid communication with at least one secondary channel, the secondary channel being helical in the circumferential area of the thorn leaking.

hereby is achieved that the individual streams in front of the fine distributor radially and mixed axially. The compact design and forced operation minimized the width of the residence time spectrum of the melt particles. Farther A fast color change is possible without a manual change To clean the tool.

The Feinverteilelement can also replace a screen basket, a sieve plate be. But it can also be used a radial distributor, this is pressed the melt in a defined annular gap. The execution of this Annular gap can also be that of a hanger or heart curve distributor correspond. (The operation of the Pinole or Herzkurvenverteiler is based on feeding through a channel.)

Advantageous It is also when the secondary channel in the penetration depth in the peripheral surface for End of the channel decreases steadily and the gap between the Vorverteilelement, So the mandrel and the fine distribution element also gets smaller, so decreases. But it is also conceivable, the channel and / or the gap to keep constant or change Channel and / or gap to perform unsteady.

In Extrusion direction is therefore the available for the melt Total cross section smaller, the pressure gradient is increased and thus the melt is controlled to the fine distributor and passed over this directed to the melt outlet. By this homogenization can be stable and reproducible conditions are created, in particular pipes of consistent quality to manufacture. By this homogenization can before the fine distributor stable and reproducible conditions are created to repercussions to minimize pre-distribution to product quality.

In addition are Advantages conceivable, if to the existing channel another channel is arranged as a secondary channel, which distributes the melt in two ways. If one considers the melt flow in the extrusion direction, then similar to the main channel one turn once on the right and once on the left around the thorn, wherein at least once a crossing point impinges on the melt flow to blur. Here, the slope of both channels can be different Therefore, the intersection point must be not necessarily in half of the circumference.

In The drawings schematically show an embodiment of the device according to the invention shown.

1 shows a perspective view in partial section and

2 a longitudinal section through the device

In 1 is a perspective view of the extrusion tool 1 to see. Looking at the melt flow in the extrusion direction, it passes from an extruder, not shown on the not visible in this view melt input 2 , via a pre-distribution element 4 and a fine distribution element 5 to the melt output 3 over which in this case the tube is extruded.

The pre-distribution element 4 is as a dome 6 executed and has a main channel 7 , also not shown, in this case with several secondary channels 8th is in fluid communication. The secondary channels 8th occur on the circumference of the thorn 6 out and run in the extrusion direction initially helically along the peripheral surface 9 of the thorn 6 , wherein the penetration depth decreases and consequently the secondary channels 8th on the peripheral surface 9 leak.

In 2 the device is shown in longitudinal section, wherein the melt input 2 right and the melt output 3 is executed on the left, the extrusion direction thus runs from right to left. Here is clearly the thorn 6 with its main channel 7 and the adjoining side channels 8th to see. The secondary channels 8th ends in the peripheral area 9 of the thorn, then adds a Feinverteilelement 5 on - here a screen basket - over which the melt to the melt output 3 arrives.

1

extrusion die

2

melt input

3

melt output

4

Vorverteilelement

5

fine distribution

6

mandrel

7

main channel

8th

secondary channel

9

Peripheral surface of the mandrel 6

Claims (4)

Device for distributing plastic Plastic compound in an extrusion tool ( 1 ), in particular pipe extrusion tool, comprising a melt input ( 2 ) and at least one melt outlet ( 3 ), wherein between melt input ( 2 ) and melt output ( 3 ) first a Vorverteilelement ( 4 ) and then a fine distribution element ( 5 ) is arranged in the form of a screen basket, characterized in that the pre-distribution element ( 4 ) as a dome ( 6 ) and a main channel ( 7 ) with at least one secondary channel ( 8th ) is in fluid communication with the secondary channel ( 8th ) helically in the peripheral surface ( 9 ) of the thorn ( 6 ) expires. Apparatus according to claim 1, characterized in that the depth of the secondary channel ( 8th ) the extent ( 9 ) of the spine ( 6 ) remains constant towards the end of the channel, steadily decreasing or decreasing discontinuously. Device according to one of the preceding claims, characterized in that the gap between the pre-distribution element ( 4 ) and the fine distribution element ( 5 ) increases in the extrusion direction, remains constant or decreases. Device according to one of the preceding claims, characterized in that in addition to the first secondary channel ( 8th ) a further secondary channel is arranged in opposite directions, which also helically in the peripheral surface ( 9 ) of the thorn ( 6 ), this further sub-channel is the first sub-channel ( 8th ) at least once.